Page 561 - Textbook of Pathology, 6th Edition

principle of measuring basal acid output (BAO) and maximal 3. Tests for Mucus 545
acid output (MAO) produced by the stomach under the
influence of a variety of stimulants, and then comparing the Protein content of gastric mucus is measured, normal value
readings of BAO and MAO with the normal values. being 1.8 mg/ml. The level is increased in chronic
hypertrophic gastritis (Ménétrier’s disease).
Quantitative analysis is performed after an overnight fast.
The stomach is intubated and gastric secretion collected in 4 4. Test for Intrinsic Factor
consecutive 15-minute intervals. This unstimulated, one-hour
collection after titration for the acid concentration in it, is Intrinsic factor (IF) is essential for vitamin B absorption from
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called BAO, expressed in mEq 1-hour. Subsequently, the the small intestine. In its absence, the absorption of vitamin
stomach is stimulated to secrete maximal acid which is B is impaired as occurs in chronic atrophic gastritis and
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similarly collected for one hour and the acid content called gastric atrophy. Schilling test is used for evaluation of patients
as MAO, expressed in mEq-1-hour. Two highest 15-minute with suspected pernicious anaemia but can also be used as a
acid outputs are added and then multiplied by 2; this gives diagnostic test for pancreatic insufficiency resulting in
the peak acid output (PAO). impaired absorption of vitamin B since gastric R-binder
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The tests for gastric acid secretion are named after the protein is not cleared from intrinsic factor due to reduced
stimulants used for MAO. Some of the commonly used pancreatic proteolytic activity. Schilling test is discussed on
substances are as under: page 308.
i) HISTAMINE. Histamine was the first standard stimulant B. TESTS FOR GASTRIN
used for gastric acid secretion test. Subcutaneous injection
of histamine phosphate (0.04 mg/kg body weight) is given Circulating gastrin secreted by G-cells present in the
with simultaneous administration of antihistaminic agent to antropyloric and proximal duodenal mucosa is normally
prevent the untoward side-effects of histamine. 0-200 pg/ml. It can be tested by the following methods:
ii) HISTALOG (BETAZOLE). Subcutaneous injection of
histalog (1-15 mg/kg body weight) is preferable over 1. Serum Gastrin Levels
histamine due to fewer undesired side-effects and no need Radioimmunoassay (RIA) is the commonly used method of
for administration of antihistaminic agent. measurement of serum gastrin levels. Normal fasting values CHAPTER 20
are 20-150 pg/ml. The levels are high in:
iii) PENTAGASTRIN (PEPTAVLON). Pentagastrin is
currently the most preferred agent administered in the dose atrophic gastritis (with low gastric acid secretion);
of 6 μg/kg body weight. Its activity is similar to gastrin. Zollinger-Ellison syndrome or gastrinoma (with high
iv) INSULIN MEAL (HOLLANDER TEST). This test is gastric acid secretion); and
based on the fact that in a state of hypoglycaemia, direct vagal following surgery on the stomach.
action on the parietal cell mass is responsible for acid
secretion. Hypoglycaemia induced by intravenous insulin 2. Gastrin Provocation Tests
(15 IU soluble insulin) can be used as a test for evaluating These tests are used to differentiate between hyper-
the completeness of vagotomy. No increase in acid gastrinaemia and gastric acid hypersecretion as follows:
production should occur if the vagal resection is complete. i) SECRETIN TEST. An intravenous injection of secretin
v) TUBELESS ANALYSIS. A resin-bound dye, diagnex (1 unit/kg body weight) is given. If the serum gastrin levels The Gastrointestinal Tract
blue, is given orally. The release of dye by the action of gastric rise by more than 50% of basal value in 5-15 minutes, it is
acid and its appearance in the urine indicates the presence diagnostic of Zollinger-Ellison syndrome (gastrinoma). This
of gastric acid. The test can be repeated after giving stimulant rise does not occur in other conditions.
of gastric secretion. ii) CALCIUM INFUSION TEST. Intravenous infusion of
SIGNIFICANCE calcium (5 mg/kg per hour) is given for 3 hour. Rise in serum
Normal value for BAO is 1.5-2.0 mEq 1-hour and for MAO is gastrin levels by more than 50% of basal value is diagnostic
12-40 mEq 1-hour. In gastric ulcer, the values of BAO and of Zollinger-Ellison syndrome (gastrinoma).
MAO are usually normal or slightly below normal. CONGENITAL ANOMALIES
Higher values are found in:
duodenal ulcer; Pancreatic Heterotopia
Zollinger-Ellison syndrome (gastrinoma); and Heterotopic pancreatic tissue may present clinically as a
anastomotic ulcer.
gastric mass or may be an incidental finding. Symptomatic
Low value or achlorhydria are observed in: cases may present in newborn or later in life.
pernicious anaemia (atrophic gastritis); and
achlorhydria in the presence of gastric ulcer is highly Grossly, it is seen as a mass projecting into the gastric
suggestive of gastric malignancy. lumen, generally in the region of submucosa and less often
in the muscular layer. In most cases, the mass is located in
2. Tests for Pepsin the region of antrum or pylorus.
Microscopically, both normal mature pancreatic acinar and
Pepsin inhibitors are used for analysis of pepsin derived from ductal tissue are seen. Islets are seen in about a third of
pepsinogen for research purposes. The levels of pepsin are cases.
low in atrophic gastritis.